Systems and Methods for Parallel Signal Cancellation

ABSTRACT

A receiver includes a first finger that receives a non-interference-cancelled signal and output first demodulated data, a first phase estimate, and a first PN code. The receiver also includes a second finger that selectively receives the non-interference-cancelled signal and a first interference-cancelled signal generated from the non-interference-cancelled signal based on the first phase estimate and the first PN code. The second finger also outputs second demodulated data.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application60/445,243 (filed Feb. 6, 2003), which is herein incorporated byreference. This application is also a continuation-in-part of U.S.patent application Ser. No. 10/699,954 (filed Sep. 23, 2003; the “'954application”), Ser. No. 10/686,828 (filed Oct. 15, 2003; the “'828application”), Ser. No. 10/686,829 (filed Oct. 15, 2003; the “'829application”), Ser. No. 10/699,360 (filed Oct. 31, 2003; the “'360application”), Ser. No. 10/294,834 (filed Nov. 15, 2002; the “'834application”), Ser. No. 10/686,359 (filed Oct. 15, 2003; the “'359application”) and Ser. No. 10/763,346 (filed Jan. 23, 2004; the “'346application”), which are all hereby incorporated by reference. Thisapplication is also related to Ser. No. 09/988,219 (filed Nov. 19, 2001;the “'219 application”), which is hereby incorporated by reference.

BACKGROUND

1. Field of the Invention

The invention generally relates to the field of communications. Morespecifically the invention is related to interference suppression foruse in coded signal communications, such as Code Division MultipleAccess (“CDMA”) communications.

2. Discussion of the Related Art

Interference in communications obstructs the intended reception of asignal and is a persistent problem. Interference may exist in manyforms. In CDMA communications, for example, interference is typicallythe result of receiving one or more unwanted signals simultaneously witha selected signal. These unwanted signals may disrupt the reception ofthe selected signal because of mutual interference. This disruption ofthe selected signal is typical in CDMA telephony systems and may corruptdata retrieval processes of a selected signal.

In CDMA telephony, a communications system typically includes aplurality of “base stations” providing a coverage area within ageographic region. These base stations communicate with mobiletelephones and/or other CDMA devices operating within the coverage area.To illustrate, a base station provides a coverage “cell” within theoverall communication coverage area maintained by the communicationssystem. While within a particular cell, a mobile telephone, or“handset”, can communicate with the base station providing the coveragefor that cell. As the mobile telephone moves to the cell of another basestation, communications between the mobile telephone and the basestation providing the initial cell coverage can be transferred via a“hand off” to the other base station.

Each base station within a CDMA telephony system uses coded signals tocommunicate with mobile telephones. For example, typical CDMA telephonysystems use pseudorandom number (PN) spreading codes, sometimes referredto as “short codes,” to encode data signals. These encoded data signalsare transmitted to and from mobile telephones to convey digitized voiceand/or other forms of communication. PN codes are known to those skilledin the art. The terms coded signals and encoded signals areinterchangeably used herein.

To encode the data signals, the base station applies a PN code to thedata at a rate faster than that of the data. For example, the PN code isapplied to the data such that there are multiple “chips” of the code forany given element of data. Such an application of the PN code iscommonly referred to as direct sequence spreading of the data. Chips andtheir associated chip rates are known to those skilled in the art.

Sometimes, each base station is assigned a particular timing offset ofthe short code to differentiate between base stations. Mobile telephonesmay therefore determine the identity of a particular base station basedon the timing offset of the short code. Additionally, the data signalsare often further encoded with a unique “covering” code. Such coveringcodes provide “channelization” for a signal that increases the number ofunique communication channels. For example, data encoded with a coveringcode can further differentiate signals thereby improving detection andsubsequent processing of a selected signal.

These covering codes are often used in CDMA telephony systems andtypically include families of codes that are orthogonal (e.g., Walshcodes) or codes that are substantially orthogonal (e.g. quasi-orthogonalfunctions (“QOF”)). Orthogonal covering codes and QOF covering codeshave properties that allow for the differentiation of unwanted signalsand are known to those skilled in the art. Walsh codes are also known tothose skilled in the art.

Both the short codes and the covering codes assist in the detection of aselected signal. However, interference caused by other signals may stilldegrade data extraction capabilities of the selected signal. Forexample, as a mobile telephone communicates with a particular basestation within that base station's coverage cell, signals from otherbase stations can interfere with the mobile telephone communication.Since cells often overlap one another to ensure that all desiredgeographic regions are included in the communication system's coveragearea, one or more signals from one base station may interfere with thecommunication link, or “channel,” between the mobile telephone andanother base station. This effect is commonly referred to ascross-channel interference.

Cross-channel interference may also occur because some overhead channelsare broadcast to all mobile telephones within the cell. These channelscan “bleed” over into other cells and overpower a selected signal,thereby corrupting conveyed data. Examples of such channels includepilot channels, which are often broadcast at greater power levels andconvey reference information and can be used to coherently demodulateother channels. Other potentially interfering channels may convey pagingchannels that alert a particular mobile telephone to an incoming calland synchronization channels that provides synchronization between amobile telephone and a base station. Still other potentially interferingchannels may include traffic channels bearing user traffic such as dataand voice.

Still, other forms of interference may occur from “multipath” copies ofa selected signal. Multipath can create interference because of thereception of copies of a selected signal at differing times. Multipathtypically occurs because of obstructions, such as buildings, trees, etcetera, that create multiple transmission paths for a selected signal.These separate transmission paths may have unique distances that causethe signal to arrive at a receiver at differing times and is commonlyreferred to as co-channel interference. Additionally, these separatepaths may bleed over into other cells to cause cross-channelinterference.

Multipath creates co-channel interference because, among other reasons,the orthogonality of the covering code for a received signal isessentially lost due to timing offsets associated with the multipath.For example, a multipath signal having a covering code and arriving at areceiver at differing times causes a misalignment of the covering code.Such a misalignment can result in a high cross-correlation in thecovering codes and a general inability to correctly retrieve conveyeddata.

“Rake” receivers, such as those used in CDMA telephony systems, combinemultipath signals to increase available signal strength. For example, arake receiver may have a plurality of “fingers,” wherein each finger ofthe rake receiver independently estimates channel gain and other signalcharacteristics (e.g., phase) of the selected signal to more accuratelydemodulate data of the selected signal and subsequently retrieve thedata. Each finger is assigned a particular “path” of the selected signal(i.e., one of the paths of the multipath signal or a signal from anotherbase station). These paths may be combined to increase signal strength.Additionally, as signal characteristics change, the fingers may beassigned or de-assigned to other “paths” of the signal to improve dataretrieval.

Rake receivers can improve data retrieval of a received signal. However,present rake receivers do not substantially reduce cross-channelinterference and/or co-channel interference. These interferers may stillcorrupt data as long as they exist in any substantial form.

SUMMARY

The present invention provides systems and methods for parallelinterference suppression. In one embodiment of the invention, aprocessing engine is used to substantially cancel a plurality ofinterfering components within a received signal. The processing engineincludes a plurality of matrix generators that are used to generatematrices, each matrix comprising elements of a unique component selectedfor cancellation. The processing engine also includes one or moreprocessors that use the matrices to generate cancellation operators. Aplurality of applicators applies the cancellation operators to parallelbut not necessarily unique input signals to substantially cancel theinterfering components from the input signals. These input signals mayinclude received signals, interference cancelled signals and/or PNcodes. The embodiments disclosed herein may be particularly advantageousto systems employing CDMA (e.g., such as cdmaOne and cdma2000), WidebandCDMA, Broadband CDMA and Global Positioning System (“GPS”) signals. Suchsystems are known to those skilled in the art.

In one embodiment of the invention, a processing engine comprises:

a plurality of matrix generators, wherein each matrix generator isconfigured for generating a matrix comprising elements of an interferingsignal selected for cancellation;

a processor communicatively coupled to the matrix generators andconfigured for generating a cancellation operator from each matrix; and

a plurality of applicators, wherein each applicator is communicativelycoupled to the processor and configured for applying one of thecancellation operators to an input signal to substantially cancel one ofthe interfering signals.

In another embodiment of the invention, the processing engine isconfigurable with a receiver and wherein the processing engine furthercomprises a connection element configured for receiving output signalsfrom the applicators and for selecting received said output signals asinputs to processing fingers of the receiver.

In another embodiment of the invention, the connection element comprisesa plurality of selectors wherein each selector is configured forreceiving one of the output signals and for selecting said one of theoutput signals as one of the inputs to one of the processing fingers.

In another embodiment of the invention, each selector is furtherconfigured for receiving a digitized radio signal comprising one or moreCode Division Multiple Access signals as one of the inputs to one of theprocessing fingers.

In another embodiment of the invention, each selector is furtherconfigured for receiving a digitized radio signal comprising one or moreWideband Code Division Multiple Access signals as one of the inputs toone of the processing fingers.

In another embodiment of the invention, each selector is furtherconfigured for receiving a digitized radio signal comprising one or moreGlobal Positioning System signals as one of the inputs to one of theprocessing fingers.

In another embodiment of the invention, the output signals areinterference cancelled signals.

In another embodiment of the invention, each cancellation operator is aprojection operator configured for projecting a selected signalsubstantially orthogonal to one of the interfering signals.

In another embodiment of the invention, the projection operatorcomprises the form:

P _(s) ^(⊥) =I−S(S ^(T) S)⁻¹ S ^(T),

where P_(s) ^(⊥) is the projection operator, I is an identity matrix, Sis one of the matrices and S^(T) is a transpose of said one of thematrices.

In another embodiment of the invention, each of the cancellationoperators comprises the form:

y′=y−S(S ^(T) S)⁻¹ S ^(T) y,

where y′ is an output cancelled signal, y is a received signal, S is oneof the matrices and S^(T) is a transpose of said one of the matrices.

In another embodiment of the invention, the processing engine furthercomprises an interference selector configured for selecting theinterfering signals as inputs to the matrix generators.

In another embodiment of the invention, the interference selector isfurther configured for providing on-time interfering PN codes of theinterfering signals to the matrix generators.

In another embodiment of the invention, the interference selectorselects the interfering signals based on a pre-determined criteriaselected from a group consisting of amplitude, timing offset, phase andcode sequence.

In one embodiment of the invention, a method of canceling interferencecomprises:

generating a plurality of matrices, each matrix comprising elements ofan interference signal selected for cancellation;

generating a cancellation operator from each of the matrices; and

applying each cancellation operator in parallel to an input signal tosubstantially cancel one of the interference signals.

In another embodiment of the invention, generating the cancellationoperator comprises generating a projection operator having a form:

P _(s) ^(⊥) =I−S(S ^(T) S)⁻¹ S ^(T),

where P_(s) ^(⊥) is the projection operator, I is an identity matrix, Sis one of the matrices and S^(T) is a transpose of said one of thematrices.

In another embodiment of the invention, applying comprises substantiallycanceling said one of the interfering signals according to the form:

y′=y−S(S ^(T) S)⁻¹ S ^(T) y,

where y′ is an output cancelled signal, y is a received signal, S is oneof the matrices and S^(T) is a transpose of said one of the matrices.

In another embodiment of the invention, the method further comprisesselecting the interference signals for input to the matrices.

In another embodiment of the invention, the method further comprisesproviding on-time interfering PN codes of the interfering signals to thematrices in response to selecting.

In another embodiment of the invention, the method further comprisesselecting output signals generated in response to applying, forassignment of the output signals to processing fingers of a receiver.

In another embodiment of the invention, the method further comprisestransferring the output signals to the processing fingers in response toselecting said output signals as input signals to the processingfingers.

In another embodiment of the invention, the output signals areinterference cancelled signals.

In another embodiment of the invention, the method further comprisesreceiving a Code Division Multiple Access signal.

In another embodiment of the invention, the method further comprisesreceiving a Wideband Code Division Multiple Access signal.

In another embodiment of the invention, the method further comprisesreceiving a Global Positioning System signal.

In one embodiment of the invention, a mobile handset comprises:

a receiver configured for receiving a radio signal; and

a processing engine communicatively coupled to the receiver andcomprising

a plurality of matrix generators, wherein each matrix generator isconfigured for generating a matrix comprising elements of an interferingsignal selected for cancellation,

a processor communicatively coupled to the matrix generators andconfigured for generating a cancellation operator from each matrix, and

a plurality of applicators, wherein each applicator is communicativelycoupled to the processor and configured for applying one of thecancellation operators to an input signal to substantially cancel one ofthe interfering signals.

In another embodiment of the invention, the radio signal comprises aCode Division Multiple Access signal.

In another embodiment of the invention, the radio signal comprises aWideband Code Division Multiple Access signal.

In another embodiment of the invention, the radio signal comprises aGlobal Positioning System signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary coded signal processing enginein one embodiment of the invention.

FIG. 2 is a block diagram of the exemplary coded signal processingengine configurable with a receiver in one embodiment of the invention.

FIG. 3 is a block diagram of exemplary receiver circuitry.

FIG. 4 is another block diagram of exemplary receiver circuitry.

FIG. 5 is a flow chart illustrating one exemplary methodical embodimentof the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that it is not intended to limit the inventionto the particular form disclosed, but rather, the invention is to coverall modifications, equivalents, and alternatives falling within thespirit and scope of the invention as defined by the claims.

FIG. 1 is a block diagram of exemplary coded signal processing engine100 in one embodiment of the invention. Coded signal processing engine(“CSPE”) 100 is used to substantially cancel interfering components fromsignals. Examples of such interfering components include co-channelinterference and cross-channel interference typical of CDMA telephony.CSPE 100 substantially cancels selected interfering components byapplying a cancellation operator to either a received signal y orselected coded reference signals. CSPE 100 thereby generates a pluralityof output cancelled signals (i.e., labeled Output CancelledSignals_(1 . . . N), where “N” is an integer greater than one), whereinthe selected interfering components are substantially removed from thereceived signal y/coded reference signals. The coded reference signalsmay be “on-time” PN codes of signals used to decode signals selected fordemodulation. On-time as used herein refers to a particular timingalignment for a PN code. Such a timing alignment may be relevant toextracting data from a signal being tracked within a receiver.

In this embodiment, CSPE 100 includes interference selector 101 forselecting interfering components and for providing selected “on-time”interfering PN codes to matrix generators 102 of CSPE 100. Theinterference selector may select the interfering signals based onpre-determined criteria, such as amplitude, timing offset, phase and/orcode sequence. Matrix generators 102 are configured for using selectedinterfering codes and phase estimates (labeled φ_(1 . . . N) Est.)corresponding to those codes to generate matrices 103 (labeled matrices103 _(1 . . . N)). Each matrix 103 comprises one or more vectors 104(labeled matrices 104 _(1 . . . N)). Further, the vectors 104 compriseelements representing components of the interfering codes (e.g., such asthose elements described in the '346 and the '360 applications). Forexample, each vector may include elements representing a unique code ofan interfering signal (e.g., co-channel interference or cross-channelinterference). The codes are typically Walsh covering codes and on-timePN codes of selected interferers. Each interference vector is multipliedby a phase estimate of a corresponding selected interferer. Phaseestimation is exemplified in the '346 application.

As multiple vectors 104 may be used to represent multiple interferingsignals, each matrix 103 may be representative of a unique plurality ofinterfering signals. For example, matrix 103 ₁ may include a singlevector representing one interfering signal A₁ (not shown), whereasmatrix 103 ₂ may include a single vector representing anotherinterfering signal A₂ (not shown). The invention, however, is notintended to be limited to the exemplary embodiment shown herein.

CSPE 100 uses each matrix 103 to generate unique cancellation operatorsfor selective cancellation of the interfering components. Accordingly,CSPE 100 includes processor 105 configured for processing matrices 103to generate the cancellation operators. The cancellation operators maybe projection operators that are used to project selected coded signalssubstantially orthogonal to the interference (e.g., the interferencerepresented by the matrices 103) so as to substantially cancel or removethe interference from the selected coded signals. In a projectionoperator embodiment, processor 105 uses matrices 103 to generate theprojection operators according to the following form:

P _(s) ^(⊥) =I−S(S ^(T) S)⁻¹ S ^(T),  (Eq. 1)

where P_(s) ^(⊥) is the projection operator, I is an identity matrix, Sis an interference matrix 103 and S^(T) is a transpose of the matrix103. Such projection operators and their associated constructions aredescribed in the '346, the '360, the '829, the '219 and the '834applications.

CSPE 100 applies the cancellation operator to selected input signals(labeled “Input Signal”). Each applicator 106 (labeled 106 _(1 . . . N))applies one of the cancellation operators to an input signal. Eachapplication of a cancellation operator typically provides a uniqueoutput cancelled signal which is the input signal with the selectedinterfering signal substantially removed. For example, using the samesignal notations of “A” as described above, applicator 106 ₁ may apply aprojection operator P_(s) _(A1) ^(⊥) to an input signal. The projectionoperator P_(s) _(A1) ^(⊥), in this example, is generated from a matrix103 comprising an interfering component of signal A₁. Once applied tothe received signal y as the input signal, applicator 106 ₁ produces anOutput Cancelled Signal₁ that corresponds to y_(A1)′=P_(s) _(A1) ^(⊥)y,where y_(A1)′ is the received signal with the interfering component A₁substantially removed.

Similarly, applicators 106 ₂ and 106 _(N) may apply projection operatorsin parallel with applicator 106 ₁ to produce the respective uniquesignals Output Cancelled Signal₂ and Output Cancelled Signal_(N). Forexample, applicator 106 ₂ may apply a projection operator P_(s) _(A2)^(⊥) such that the applicator produces an Output Cancelled Signal₂corresponding to y_(A2)′=P_(s) _(A2) ^(⊥)y, where y_(A2)′ is thereceived signal with the interfering component A₂ substantially removed.Parallel as used herein implies the substantially simultaneousgenerations of unique cancellation operators and the subsequentapplications of the cancellation operators to independent input signals.

In an alternative embodiment, cancellation may be performed by applyinga construction of the matrices as follows:

y′=y−S(S ^(T) S)⁻¹ S ^(T) y.  (Eq. 2)

In such an embodiment, the received signal y is multiplied by theinterference matrix construction of Eq. 1. However, that product issubtracted from the received signal y to produce an output cancelledsignal y′, such as y_(A1)′ and y_(A21)′. Those skilled in the art shouldreadily recognize that the two approaches produce substantially the sameresult.

While one exemplary embodiment has been shown in detail, the inventionis not intended to be limited to the examples described and illustratedherein. For example, applicators 106 may apply other cancellationoperators to other input signals to produce a variety of outputcancelled signals. One example of another input signal is an on-timereference PN code, such as that described below in FIG. 4. Examples ofother methods for the production of cancellation operators includesubtractive methods, decorrelators and decision feedback.

Additionally, the invention is not intended to be limited to the numberof applicators 106, input signals, output cancelled signals, matrixgenerators 102 and processors 105. For example, processor 105 may beeither a single processor configured for generating a plurality ofcancellation operators or processor 105 may represent a plurality ofprocessors each of which is similarly configured for generating a uniquecancellation operator. Examples of such processors include generalpurpose processors and Application Specific Integrated Circuits(“ASIC”). Accordingly, the processor may be operably controlled viasoftware and/or firmware instructions to generate the cancellationoperators. Those skilled in the art are familiar with processors, ASICs,software, firmware and the various combinations thereof which may beused in such implementations.

Moreover, those skilled in the art should readily recognize that CSPE100 in general as described herein may be implemented through software,firmware, hardware and/or various combinations thereof. For example, thegenerations of the cancellation operators and the subsequentcancellations of interfering signals may be computed through the use ofsoftware instructions (e.g., firmware) operable within a processor orspecified in hardware architecture.

FIG. 2 is a block diagram of the exemplary CSPE 100 of FIG. 1configurable with receiver 204 in one embodiment of the invention. Inthis embodiment, receiver 204 receives a radio frequency (“RF”) signalthrough antenna 201 and subsequently converts that signal to a digitalreceived signal y using Analog-to-Digital (“A/D”) converter 202. A/Dconverter 202 transfers the digital signal to receiver circuitry 203 forsignal processing. Those skilled in the art should readily recognizethat the processing of CDMA signals typically includes both In-phase(“I”) and Quadrature (“Q”) components. As such, the digital receivedsignal y may include both I and Q components as well.

In this embodiment, receiver circuitry 203 is configured fortransferring the digitized received signal y to CSPE 100 forcancellation of interfering signals. CSPE 100 receives the signal y aswell as known codes from the interfering signals. For example, theinterfering signals may be cross channel and/or co-channel interferingsignals comprising known codes of CDMA telephony systems. Such codes maybe input to CSPE 100 on an as needed basis or stored within a memory(not shown) local to the CSPE 100. Alternatively, the codes may begenerated by processor 105 on an as needed basis.

Operable characteristics of CSPE 100 are the same as those described inFIG. 1. However, again using the same signal notations of “A” asdescribed above, in this preferred receiver embodiment, CSPE 100 usesapplicators 106 _(1 . . . N) to apply cancellation operators to theinput signals in the following manner:

Applicator 106 ₁ produces an Output Cancelled Signal₁ that correspondsto y_(A1)′=P_(s) _(A1) ^(⊥)y, where again y_(A1)′ is the received signalwith the interfering component A₁ substantially removed;

Applicator 106 ₂ produces an Output cancelled Signal₂ corresponding toy_(A2)′=P_(s) _(A2) ^(⊥)y; and where again y_(A2)′ is the receivedsignal with the interfering component A₂ substantially removed.

These Output Cancelled Signal_(1 . . . N) are transferred to connectionelement 206 via “N” channel connection 205. For example, “N” channelconnection 205 may be a communicative connection such as a data bus thatallows for the transfer of “N” number of channels to connection element206. Consequently, connection element 206 may be configurable to receivesuch an “N” channel connection.

Connection element 206 is configured for selectively transferring OutputCancelled Signal_(1 . . . N) to receiver circuitry 203 of receiver 204via “M” channel connection 207. For example, connection element 206 maybe a switching device, multiplexer, a plurality of multiplexers oranother similar communication device that selectively transfers “N”number of signals to “M” number of channels, where “M” is also a numbergreater than one. As such, “M” channel connection 207 is similar to “N”channel connection 205.

The control for connection element 206 may be applied independently ofcancellation processing. Consequently, connection element 206 may or maynot be configured within the CSPE 100. For example, should the selectionof Output Cancelled Signal_(1 . . . N) be received by receiver circuitry203 be decided by receiver 204, then connection element 206 may resideoutside of the embodied CSPE 100. In a preferred embodiment, however,CSPE 100 includes the control functionality for connection element 206that determines which of the Output Cancelled Signal_(1 . . . N) aretransferred to receiver circuitry 203. Accordingly, the invention shouldnot be limited to the preferred embodiment described and shown herein.

FIG. 3 is a block diagram of exemplary receiver circuitry 203. In thisembodiment, receiver circuitry 203 is configured with CSPE 100 viaconnection element 206 for selectively tracking signals through receiverfingers f1, f2 and f3 (labeled 302 _(f1), 302 _(f2) and 302 _(f3)). Forexample, connection element 206 may allow the receiver circuitry 203 totrack and subsequently demodulate a selected combination of OutputCancelled Signal_(1 . . . N) and the received signal y through thereceiver fingers f1, f2 and f3.

In a preferred embodiment, a first receiver finger f1 receives thesignal y via a corresponding selector (the selectors are labeled 301_(f1 . . . f3)). The phase estimate φ_(f1) and the PN code_(f1) outputsof the first receiver finger f1 are transferred from the finger to CSPE100 for producing the output cancelled signal y_(A1)′ described in FIGS.1 and 2. A second receiver finger f2 selectively receives either y ory_(A1)′ via a corresponding selector for tracking of a second assignedsignal. If y is transferred to the second receiver finger f2, the phaseestimate φ_(f2) and the PN code_(f2) outputs of that second receiverfinger are transferred to CSPE 100 to produce the output cancelledsignal y_(A2)′ also described in FIGS. 1 and 2. Consequently, a thirdreceiver fingers f3 has a selection of signals y and output cancelledsignals y_(A1)′ and y_(A2)′ to track and demodulate a third assignedsignal.

In many instances, tracking, demodulation and cancellation of thesignals described and shown herein the preferred embodiment is all thatis necessary in CDMA telephony because there are typically only one ortwo signals (e.g., A1 and A2) that degrade reception beyond the point ofintended data recovery. Accordingly, selective cancellation of only oneor two signals may decrease processor consumption requirements andthereby improve overall processing performance of the system. As such,the embodiment should not be limited to the number of receiver fingersshown and described. More receiver fingers than those illustrated inthis exemplary embodiment may be used to selectively track anddemodulate signals according to the principles described herein.

FIG. 4 is another block diagram of exemplary receiver circuitry 203. Inthis alternative embodiment, the received signal y is transferred toreceiver fingers f1, f2 and f3 (labeled 405 _(f1 . . . f3)) and CSPE100. Time tracking and phase estimation of the received signal y may beperformed for each finger in corresponding elements 401 _(f1 . . . f3).Such tracking and phase estimation is used to generate on-time referencePN codes (PN code_(f1 . . . f3)) and is described in greater detail inthe '346 application. Elements 401 _(f1 . . . f3) transfer the on-timereference PN codes as well as the phase estimates (labeledφ_(f1 . . . f3)) to CSPE 100 and to corresponding selectors 402_(f1 . . . f3). CSPE 100 uses these on-time PN codes and phase estimatesto generate cancellation operators that remove interfering signals fromthe received signal y.

Differing from the embodiment of FIG. 3, CSPE 100 uses the applicators106 of FIGS. 1 and 2 to apply cancellation operators to the on-time PNcodes to produce output cancelled versions of the codes (labeled outputreference codes). Such an embodiment may conform to a cancellation ofthe form P_(s) ^(⊥)x, where x is an on-time reference PN code. Theseoutput cancelled reference codes are selectively transferred todemodulators 403 _(f1 . . . f2) via selectors 402 _(f1 . . . f2) ofconnection element 206. These codes are used by the demodulators 403_(f1 . . . f2) to demodulate the received signal y. Such demodulationmay be performed with a correlation of a reference code and a receivedsignal over a period of a symbol and is well known to those skilled inthe art.

In a preferred embodiment, a first receiver finger f1 receives theon-time reference PN code x_(f1) via a first selector 402 _(f1) andproduces the phase estimate φ_(f1) the PN code_(f1) outputs. The firstfinger f1 then demodulates the received signal y using the code x_(f1).These phase estimate φ_(f1) and the PN code_(f1) outputs of that firstreceiver finger f1 may be transferred from the finger f1 to CSPE 100 forproducing the output cancelled signal x_(A1)′, where x_(A1)′ is theon-time reference PN code of the signal selected for demodulationwithout the interfering effects of the signal A1. A second receiverfinger f2 selectively receives either x or x_(A1)′ via correspondingselector 402 _(f2). If x is transferred to the second receiver fingerf2, the phase estimate φ_(f2) and the PN code_(f2) outputs of receiverfinger f2 are transferred to CSPE 100 to produce the output cancelledsignal x_(A2)′, where x_(A2)′ is the on-time reference PN code of thesignal selected for demodulation without the interfering effects of thesignal A2. Consequently, a third receiver finger f3 has a selection ofsignals x_(f3) and output cancelled on-time reference PN codes x_(A1)′and x_(A2)′ which can be used to track and demodulate the receivedsignal y.

Again, those skilled in the art should readily recognize that thepreferred embodiment should not be limited to that which is shown anddescribed herein. More receiver fingers than those illustrated anddescribed herein the exemplary embodiment may be used to selectivelytrack and demodulate signals according to the principles describedherein.

FIG. 5 is a flow chart 500 illustrating one exemplary methodicalembodiment of the invention. In this embodiment, one or moreinterference components of a received signal are selected, in element501. These interference components are used to generate an interferencematrix, in element 502. A cancellation operator is generated from theinterference matrix, in element 503. The cancellation operator may be aprojection operator as described in FIG. 1 that is generated in element504 to substantially orthogonally project a received signal frominterfering components. Such a projection operator may substantiallycancel or remove the interfering components from the received signal.The cancellation operator is applied to either the received signal or anon-time reference PN code, in element 505.

Elements 501 through 505 are performed in parallel based on the numberof receiver fingers used for tracking and demodulation in a receiver.For example, in a receiver comprising three fingers, such as thereceiver circuitry 203 in FIGS. 4 and 5, elements 501 through 505 may beperformed three times in a substantially simultaneous fashion. Moreover,control functionality may be configured to only select information ofparticular fingers. For example, if a signal does not contributesignificantly to the interference, it may be selectively excluded fromthe cancellation process to decrease processing. Such a selectionprocess is described in the '954 application.

The application of the cancellation operators in element 505 producesoutput cancelled signals such as those described herein. Once thoseoutput cancelled signals are produced, the signals are selected forfinger assignments, in element 506. Such a selection process may beperformed by connection element 206 in FIG. 3. Selected output cancelledsignals are transferred to the receiver fingers according to theirrespective finger assignments, in element 507. Within their respectivefingers, the output cancelled signals are either tracked and demodulatedas in FIG. 3 or are used to track and demodulate a received signal as inFIG. 4.

The embodiments described herein may substantially reduce interferencecaused by unwanted signals and improve signal processing. For example,poor signal quality due to interference may deleteriously affectacquisition, tracking and demodulation of selected signals. A reductionof interference May, therefore, result in improved signal processing anderror reduction. In regards to such benefits, the embodiments herein mayadvantageously require use within a CDMA telephony system. Improvedprocessing within a CDMA telephony system may be exploited in terms ofincreased system capacity, transmit power reduction, system coverageand/or data rates. However, those skilled in the art should readilyrecognize that the above embodiments should not be limited to anyparticular method of signaling. For example, the embodiments disclosedherein may also be advantageous to systems employing CDMA (e.g., such ascdmaOne and cdma2000), WCDMA, Broadband CDMA and GPS signals.

Additionally, it should be noted that the above embodiments of theinvention may be implemented in a variety of ways. For example, theabove embodiments may be implemented from software, firmware, hardwareor various combinations thereof. Those skilled in the art are familiarwith software, firmware, hardware and their various combinations. Toillustrate, those skilled in the art may choose to implement aspects ofthe invention in hardware using ASIC chips, Digital Signal Processors(“DSP”) and/or other integrated circuitry (e.g., custom designedcircuitry and Xilinx chips). Alternatively, aspects of the invention maybe implemented through combinations of software using Java, C, C++,Matlab, and/or processor specific machine and assembly languages.Accordingly, those skilled in the art should readily recognize that suchimplementations are a matter of design choice and that the inventionshould not be limited to any particular implementation.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and description isto be considered as exemplary and not restrictive in character.Accordingly, it should be understood that only the preferred embodimentand minor variants thereof have been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

1. A receiver comprising: a first finger configured to receive a non-interference-cancelled signal and output first demodulated data, a first phase estimate, and a first PN code; and a second finger configured to: selectively receive the non-interference-cancelled signal and a first interference-cancelled signal generated from the non-interference-cancelled signal based on the first phase estimate and the first PN code; and output second demodulated data. 